Thank you for reaching out to the Community. I apologize your alt text is not visible on images in the editor after copying your emails. This is actually something our upper level of support is looking into further. Although the alt text is not visible in the editor, it is still present in the email. If you would like the text to always be visible, as a work around we suggest entering it in the Description field of your image under the Library tab of your account.
We have also added you to our queue to be notified when this is resolved.
Frankie P. Community & Social Media Support
Did I answer your question? If so, please mark my post as an "Accepted Solution" by clicking the Accept as Solution button in the bottom right hand corner of this post.